Effect of inoculum size on detection of Candida growth by the BACTEC 9240 automated blood culture system using aerobic and anaerobic

Simulated candidemia was produced with 20 Candida isolates at three inoculum sizes (100, 10, and 1 CFU/ml of blood). Growth detection was better with larger inocula. The time to growth detection was shorter with larger inocula. Inoculum size does effect Candida growth detection and time to detection in BACTEC 9240 automated systems. Candida species rank fourth among organisms isolated from the blood of hospitalized patients, with non-albicans Candida species accounting for about 50 % of these Candida isolates (1, 2, 5, 9, 11, 14). Most hospitals rely on automated blood culture systems for the detection of blood pathogens, including Can-dida spp. The College of American Pathologists recommends that blood cultures be incubated for 5 days and then discarded without terminal subculture if growth is not detected by the automated system. In two previous studies of simulated candi-demia with the BACTEC 9240 automated blood culture sys-tem (Becton Dickinson and Co., Sparks, Md)., we noted poo